/*_############################################################################
  _## 
  _##  SNMP4J 2 - Null.java  
  _## 
  _##  Copyright (C) 2003-2011  Frank Fock and Jochen Katz (SNMP4J.org)
  _##  
  _##  Licensed under the Apache License, Version 2.0 (the "License");
  _##  you may not use this file except in compliance with the License.
  _##  You may obtain a copy of the License at
  _##  
  _##      http://www.apache.org/licenses/LICENSE-2.0
  _##  
  _##  Unless required by applicable law or agreed to in writing, software
  _##  distributed under the License is distributed on an "AS IS" BASIS,
  _##  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  _##  See the License for the specific language governing permissions and
  _##  limitations under the License.
  _##  
  _##########################################################################*/
package org.snmp4j.smi;

import java.io.*;
import org.snmp4j.asn1.BER;
import org.snmp4j.asn1.BERInputStream;
import org.snmp4j.asn1.BER.MutableByte;

/**
 * The <code>Null</code> class represents SMI Null and the derived
 * SMIv2 exception syntaxes.
 *
 * @author Frank Fock
 * @version 1.8
 */
public class Null extends AbstractVariable {

    private static final long serialVersionUID = 6907924131098190092L;

    private int syntax = SMIConstants.SYNTAX_NULL;

    public static final Null noSuchObject = new Null(SMIConstants.EXCEPTION_NO_SUCH_OBJECT);
    public static final Null noSuchInstance = new Null(SMIConstants.EXCEPTION_NO_SUCH_INSTANCE);
    public static final Null endOfMibView = new Null(SMIConstants.EXCEPTION_END_OF_MIB_VIEW);
    public static final Null instance = new Null(SMIConstants.SYNTAX_NULL);

    public Null() {
    }

    public Null(int exceptionSyntax) {
        setSyntax(exceptionSyntax);
    }

    public void decodeBER(BERInputStream inputStream) throws java.io.IOException {
        MutableByte type = new BER.MutableByte();
        BER.decodeNull(inputStream, type);
        this.syntax = type.getValue() & 0xFF;
    }

    public int getSyntax() {
        return syntax;
    }

    public int hashCode() {
        return getSyntax();
    }

    public int getBERLength() {
        return 2;
    }

    public boolean equals(Object o) {
        return (o instanceof Null) && (((Null) o).getSyntax() == getSyntax());
    }

    public int compareTo(Variable o) {
        return (getSyntax() - o.getSyntax());
    }

    public String toString() {
        switch (getSyntax()) {
            case SMIConstants.EXCEPTION_NO_SUCH_OBJECT:
                return "noSuchObject";
            case SMIConstants.EXCEPTION_NO_SUCH_INSTANCE:
                return "noSuchInstance";
            case SMIConstants.EXCEPTION_END_OF_MIB_VIEW:
                return "endOfMibView";
        }
        return "Null";
    }

    public void encodeBER(OutputStream outputStream) throws java.io.IOException {
        BER.encodeHeader(outputStream, (byte) getSyntax(), 0);
    }

    public void setSyntax(int syntax) {
        if ((syntax != SMIConstants.SYNTAX_NULL) && (!isExceptionSyntax(syntax))) {
            throw new IllegalArgumentException("Syntax " + syntax + " is incompatible with Null type");
        }
        this.syntax = syntax;
    }

    public Object clone() {
        return new Null(this.syntax);
    }

    public static boolean isExceptionSyntax(int syntax) {
        switch (syntax) {
            case SMIConstants.EXCEPTION_NO_SUCH_OBJECT:
            case SMIConstants.EXCEPTION_NO_SUCH_INSTANCE:
            case SMIConstants.EXCEPTION_END_OF_MIB_VIEW:
                return true;
        }
        return false;
    }

    /**
     * Returns the syntax of this Null variable.
     * @return
     *    {@link SMIConstants#SYNTAX_NULL} or one of the exception syntaxes
     *    {@link SMIConstants#EXCEPTION_NO_SUCH_OBJECT},
     *    {@link SMIConstants#EXCEPTION_NO_SUCH_INSTANCE}, or
     *    {@link SMIConstants#EXCEPTION_END_OF_MIB_VIEW}
     * @since 1.7
     */
    public final int toInt() {
        return getSyntax();
    }

    /**
     * Returns the syntax of this Null variable.
     * @return
     *    {@link SMIConstants#SYNTAX_NULL} or one of the exception syntaxes
     *    {@link SMIConstants#EXCEPTION_NO_SUCH_OBJECT},
     *    {@link SMIConstants#EXCEPTION_NO_SUCH_INSTANCE}, or
     *    {@link SMIConstants#EXCEPTION_END_OF_MIB_VIEW}
     * @since 1.7
     */
    public final long toLong() {
        return getSyntax();
    }

    public OID toSubIndex(boolean impliedLength) {
        throw new UnsupportedOperationException();
    }

    public void fromSubIndex(OID subIndex, boolean impliedLength) {
        throw new UnsupportedOperationException();
    }
}
